CONSERVATION MONITORING OF A HERITAGE CEILING BY PHOTOMETRIC STEREO

Abstract. Photographic survey techniques were employed to monitor the condition of the paintwork on the ceiling of the Queen's Staircase at Hampton Court Palace. Illumination was provided by a flash, mounted on an 8 metre telescopic mast, raised to approximately 60 cm below the ceiling, with images were taken from a fixed camera position on the floor of the landing at a range of 6.5 m. The photometric stereo method was applied to images from ten lamp positions, to calculate surface normals and a depth map. Cross-sections at the estimated surface resolution of 7.7 pixels/mm, achieved a depth (Z axis) resolution of approximately 100 microns.